The involvement of regional lymph nodes with tumor may be the most important prognostic indicator in breast cancer. However, little work has been done in investigating the immunologic aspects of the regional lymph node cells (RLNC) in this disease. A histopathologic correlation has been suggested between prognosis and sinus histiocytosis which may be indicative of a local immune response. Other studies indicate an antegenic stimulation of the RLNC closest to the tumor. Most in vitro studies have stressed the immunologic competence of RLNC. However, little has been done on cell-mediated immune responses specific for breast cancer associated antigens. Recent work demonstrates inhibition of leukocyte migration with RLNC that was greater than with peripheral blood cells using a crude breast cancer homogenate antigen. These studies suggest the need to test the in vitro reactivity of RLNC in order to ascertain its usefulness in predicting recurrence of breast cancer. This project would be designes for that purpose.